In most foundry operations, hot metal is poured into a mold cavity produced by a pattern. The mold cavity is sometimes produced by compressing sand and clay binders together with water to produce a formable mixture which will retain the shape of the pattern. In other processes, the pattern is surrounded by sand which has been treated with a resin binder, which binder hardens in air within a relatively short period of time. Occasionally metal cores and metal rods are used to reinforce the mold, such rods and cores being embedded in the sand at appropriate places.
Because of the increased costs of the sand and other materials used in forming a mold, and because of the cost of disposing of such materials if they are considered scrap, the foundry industry has been faced with the problem of reclaiming sand for reuse in molding operations. The practice heretofore has been simply to place the sand, after the casting has been removed, onto a vibratory screen or other screening apparatus provided with horizontal decks, through which the sand particles pass for reuse. In such processes, only a portion of the sand is recovered for reuse and a good deal still results as waste or scrap material.